2. CONTENTS
Introduction
Definition
Example of WSN
Types of WSN
Characteristics of a
WSN
Power saving protocols
for WSN
Applications
Challenges
Advantages
Disadvantages
Future Scope
Conclusion 2
3. INTRODUCTION
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Low power wireless sensor Networks are
networks that consists of sensors which are
distributed in an ad hoc manner.
These sensors work with each other to sense
some physical phenomenon and then the
information gathered is processed to get relevant
results.
Low power Wireless sensor networks consists of
protocols and algorithms with self-organizing
capabilities.
4. CONTINUED.........
Sensor networks are highly distributed networks of small,
lightweight wireless node, deployed in large numbers to
monitor the environment or system.
Each node of the sensor networks consist of three subsystem:
Sensor subsystem: senses the environment
Processing subsystem: performs local computations on the
sensed data
Communication subsystem: responsible for message exchange
with neighboring sensor nodes
The features of sensor nodes
Limited sensing region, processing power, energy
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5. 5
DEFINITION
Low power Wireless Sensor Networks :
Highly distributed networks of small, lightweight wireless
nodes,
Deployed in large numbers,
Monitors the environment or system by measuring phys
parameters such as temperature, pressure, humidity.
Node:
sensing + processing + communication
7. TYPES OF WIRELESS SENSOR NETWORKS
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Dense collection of nodes
Ad-hoc
deployment
Difficulty in network
maintenance
Few and scarcely
distributed nodes
Pre-planned deployment
Lower network
maintenance
Unstructured WSN Structured WSN
8. CHARACTERISTICS OF A LPWSN
1. Self – Organization
2. Concurrency processing
3. Low cost
4. Restricted energy resources
5. Tiny
6. Small radio range 8
9. 9
POWER SAVING PROTOCOLS
THERE ARE SOME PROTOCOLS WHICH IS USED
FOR POWER SAVING……..
Unified Network Protocol Framework (UNPF)
Low-Energy Adaptive Clustering Hierarchy
(LEACH)
MAC PROTOCOL
NETWORK LAYER
BATTERY MODEL
and some other…
10. 10
LAYERED ARCHITECTURE
A single powerful base station
(BS)
Layers of sensor nodes around
BS
Layer i: All nodes i-hop away
from BS
Applications:
In-building: BS is an access point
Military
Short-distance, low power tt tx
11. 11
UNIFIED NETWORK PROTOCOL
FRAMEWORK (UNPF)
A layered architecture
A set of protocols
Integrates three operations:
Network Initialization & Maintenance Protocol
MAC Protocol
Routing Protocol
12. 12
UNIFIED NETWORK PROTOCOL
FRAMEWORK (UNPF)
Network Initialization & Maintenance Protocol:
BS broadcasts its ID using CDMA common control channel
(BS reaches all nodes in one hop)
Nodes record BS ID & send beacon signal with their own
IDs at their low default power levels
All nodes the BS can hear are at 1-hop distance
The BS broadcasts a control packet with all layer one node
IDs
All nodes send a beacon signal again
The layer one nodes record the IDs they hear-layer 2
The layer one nodes inform the BS of the layer 2
The BS broadcasts the layer2 nodes IDs,…
To maintain: periodic beaconing updates are required
13. 13
POWER SAVING MODE
Turning the transceiver off may not always be
efficient. Operation in a power-saving mode is
energy-efficient only if the time spent in that mode
is greater than a certain threshold
MULTIPLE HOPS
Using several short hops may be more energy
efficient than using one large hop.
14. 14
CLUSTERED ARCHITECTURE
A clustered architecture organizes the sensor nodes into clusters, each
governed by a cluster-head. The nodes in each cluster are involved in
message exchanges with their cluster-heads, and these heads send message
to a BS.
Clustered architecture is useful for sensor networks because of its inherent
suitability for data fusion. The data gathered by all member of the cluster
can be fused at the cluster-head, and only the resulting information needs to
be communicated to the BS.
The cluster formation and election of cluster-heads must be an autonomous,
distributed process.
16. 16
LOW-ENERGY ADAPTIVE CLUSTERING HIERARCHY
(LEACH)
Self-organizing and adaptive clustering protocol
Evenly distributes the energy expenditure among
the sensors
Performs data aggregation where cluster heads
act as aggregation points
Two main phases:
Setup phase: organizing the clusters
Steady-state phase: deals with the actual data
transfers to the BS
17. 17
Setup phase:
Each sensor chooses a random number m between 0 and 1
If m < T(n) for node n, the node becomes a cluster-head where
P : the desired percentage of cluster heads
r : the round number
G : the set of nodes that have not been cluster heads during the last
1 / P rounds
A cluster head advertises its neighbors using a CSMA MAC.
Surrounding nodes decide which cluster to join based on the signal
strength of these messages
Cluster heads assign a TDMA schedule for their members
1 [ * mod(1/ )]( )
0 ,
P
if n G
P r PT n
otherwise
18. 18
Steady-state phase:
All source nodes send their data to their cluster heads
Cluster heads perform data aggregation/fusion through
local transmission
Cluster heads send them back to the BS using a single
direct transmission
After a certain period of time, cluster heads are selected
again through the set-up phase
19. 19
LOW-ENERGY ADAPTIVE CLUSTERING
HIERARCHY (LEACH)
Merits:
Accounting for adaptive clusters and rotating cluster
heads
Opportunity to implement any aggregation function at
the cluster heads
Demerits:
Highly dynamic environments
Continuous updates
Mobility
20. 20
MAC PROTOCOL
During the data transmission phase, the distributed TDMA
receiver oriented channel (DTROC) assignment MAC protocol
is used.
Two steps of DTROC :
Channel allocation : Each node is assigned a reception channel
by the BS, and channel reuse is such that collisions are avoided.
Channel scheduling : The node schedules transmission slots for
all its neighbors and broadcasts the schedule. This enables
collision-free transmission and saves energy, as nodes can turn
off when they are not involved on a send/receive operation.
21. THERE ARE THREE TYPES OF MAC
PROTOCOLS
Fixed-allocation
Demand-based
Contention-based
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22. 22
Fixed-allocation MAC protocol
Share the common medium through a predetermined assignment.
It is suitable for sensor network that continuously monitor and
generate deterministic data traffic
Provide a bounded delay for each node
However, in the case of bursty traffic, where the channel
requirements of each node may vary over time, it may lead to
inefficient usage of the channel.
23. 23
Demand-based MAC protocol
Used in such cases, where the channel is allocated according to
the demand of the node
Variable rate traffic can be efficiently transmitted
Require the additional overhead of a reservation process
Contention-based MAC protocol
Random-access-based contention for the channel when packets
need to be transmitted
Suitable for bursty traffic
Collisions and no delay guarantees, are not suitable for delay-
sensitive or real-time traffic
24. 24
HYBRID TDMA/FDMA
A pure TDMA scheme minimize the time for which a node has to be
kept on, but the associated time synchronization cost are very high.
A pure FDMA scheme allots the minimum required bandwidth for
each connection
If the transmitter consumes more power, a TDMA scheme is favored,
since it can be switch off in idle slots to save power.
If the receiver consumes greater power, a FDMA scheme is favored,
because the receiver need not expend power for time
synchronization.
26. APPLICATIONS OF LPWSN
Area monitoring
Health care monitoring
Air pollution monitoring
Forest fire detection
Landslide detection
Water quality monitoring
Natural disaster prevention
Industrial monitoring
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27. 27
Facility management
Intrusion detection into industrial sites
Control of leakages in chemical plants, …
Machine surveillance and preventive maintenance
Embed sensing/control functions into places no cable
has gone before
E.g., tire pressure monitoring
Precision agriculture
Bring out fertilizer/pesticides/irrigation only where
needed
Medicine and health care
Post-operative or intensive care
Long-term surveillance of chronically ill patients or the
elderly
29. ADVANTAGES OF A WSN
Avoids a lot of wiring
Can accommodate new devices at any time
Flexible to go through physical partitions
It can be accessed through a centralized monitor
Infrastructure
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30. DISADVANTAGES OF WSN
Easy for hackers to hack a network
Comparatively low speed of communication
Gets distracted by various elements
Costly at large
Life of nodes
Energy life 30
31. FUTURE SCOPE
More research work needs to be done in future.
Needs to be implemented in a wireless sensor network
with mobile nodes.
The effects of very large node densities need to be
investigated.
The feasibility of using the clustering technique and data
aggregation needs to be tested in the same wireless
sensor network. 31
33. 33
FUTURE OF WSN
SMART HOME / SMART OFFICE
Sensors controlling
appliances and
electrical devices in the
house.
Better lighting and
heating in office
buildings.
The Pentagon building
has used sensors
extensively.
34. FUTURE SCOPE
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Intelligent transport,
industry and society,
smart utilities
Connected
Consumer
Electronics
Development of a TDMA/CSMA hybrid MAC
TinyOS currently has a CSMA MAC
Hope to improve throughput by employing TDMA
Time is divided into transmission periods and contention perio
Nodes will contend with each other to join “the transmission
group” during the contention period.
Nodes in the transmission group will be allocated a time-slot in
the transmission period.
Development of data storage engine optimized for fast
retrieval
35. CONCLUSION
This presentation shows all the techniques that are used
for wireless sensor network for low power consumption ,
for example MAC protocol, LEACH, Network layer, ect.
Most of the research on energy efficient controlled
access protocol has come at a cost of control
packets overhead. By investigating this research
area further, an enhanced energy efficiency
protocol may be developed that can revolutionise
WSN’s power consumption.
There are some another protocols which can be used for
less energy consumption like CDMA,FDMA,TDMA.
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